This invention relates to a circuit for generating an input transition detection pulse.
Circuits adapted for detecting change of an input signal and producing an output signal of a predetermined pulse width are widely used in such applications as semiconductor memory devices. Even in cases where input transition detection pulse generator circuits (hereinafter referred to as input transition detection pulse generators depending upon circumstances), are driven by different power supply voltages according to use, they are required to meet these conditions. Namely, in the case where the power supply voltage Vcc is, e.g., more than 1.5 volts, the input transition detection pulse generator outputs, with a view to performing high speed operation, a signal such that its pulse width is not broader than a fixed value. In contrast, in the case where the power supply voltage Vcc is, e.g., lower than 1.5 volts, the input transition detection pulse generator outputs, by employing a scheme such that prevention of an erroneous operation is considered to be more preferential than high speed operation, a signal of a broader pulse width to the extent the power supply voltage Vcc decreases. To meet such requirements in operation, a designer needs to arbitrarily change the power supply voltage dependency of the pulse width.
The configuration of a conventional input transition detection pulse generator is shown in a block form in FIG. 9. To an input transition detection pulse generation unit/pulse width setting unit 141, (N+1) signals A0, A1, - - - , AN are input. When transition (change in level) is detected in at least one of these signals, a pulse signal having a predetermined pulse width is output.
As stated above, the input transition detection pulse generation unit for detecting transition of an input to generate a pulse signal and the pulse width setting unit for setting the width of this pulse signal were conventionally constituted with a single circuit 141 without taking into consideration the power supply voltage dependency of the output pulse width. For this reason, it was extremely difficult for a designer to arbitrarily set the power supply voltage dependency of the output pulse width in accordance with the use.